Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session A35: Thin Film Processing: Theory and Experiment |
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Sponsoring Units: DCMP Chair: Nuri Oncel, University of North Dakota Room: 298 |
Monday, March 13, 2017 8:00AM - 8:12AM |
A35.00001: Controlling roughening processes in the stochastic Kuramoto-Sivashinsky equation Susana Gomes, Serafim Kalliadasis, Demetrios Papageorgiou, Grigorios Pavliotis, Marc Pradas We present a novel control methodology to control the roughening processes of semilinear parabolic stochastic partial differential equations in one dimension, which we exemplify with the stochastic Kuramoto-Sivashinsky equation. The original equation is split into a linear stochastic and a nonlinear deterministic equation so that we can apply linear feedback control methods. Our control strategy is then based on two steps: first, stabilize the zero solution of the deterministic part and, second, control the roughness of the stochastic linear equation. We consider both periodic controls and point actuated ones, observing in all cases that the second moment of the solution evolves in time according to a power-law until it saturates at the desired controlled value. [Preview Abstract] |
Monday, March 13, 2017 8:12AM - 8:24AM |
A35.00002: Theory of current-induced surface roughness reduction in conducting thin films Dwaipayan Dasgupta, Lin Du, Dimitrios Maroudas Thin film surface roughness is responsible for various materials reliability problems in microelectronics and nanofabrication technologies. Aiming at a fundamental understanding of surface dynamical phenomena toward developing surface roughness reduction strategies, we report results of a systematic modeling study that establish the electrical surface treatment of conducting thin films as a viable physical processing strategy for surface roughness reduction. We develop a continuum model of surface morphological evolution that accounts for the residual stress in the deposited conductor film, surface diffusional anisotropy and film texture, the film's wetting of the layer that is deposited on, and surface electromigration. Supported by linear stability theory, self-consistent dynamical simulations based on the model demonstrate that the action over several hours of a sufficiently strong and properly directed electric field on a conducting thin film can reduce its surface roughness and lead to a smooth planar film surface. The modeling predictions are in agreement with experimental measurements on copper thin films deposited on silicon nitride layers. [Preview Abstract] |
Monday, March 13, 2017 8:24AM - 8:36AM |
A35.00003: Transparent Aluminum Oxide Films by Edge Anodization Jonathan Stott, Thomas Greenwood, David Winn In this paper we present our recent work on manufacturing thin ($3$ -- $5\,\mu\mbox{m}$) films of porous aluminum(III) oxide [PAO] using a novel edge-anodization technique. With this modified anodization process, we are able to create transparent PAO films on top of insulating substrates such as glass or plastic. By controlling the processing parameters, the index of refraction of PAO films can be engineered to match the substrate, which gives us a durable reflection-free and scratch-resistant coating over conventional optics or LCD displays. Eventually we hope to create ordered porous aluminum oxide cladding around an optical fiber core, which could have a number of interesting optical properties if the pore spacing can be matched to the wavelength of light in the fiber. [Preview Abstract] |
Monday, March 13, 2017 8:36AM - 8:48AM |
A35.00004: Low Temperature Growth of Zinc Oxide Thin Films on Polymer Substrates Using Pulsed Laser Deposition Technique Kun Tian, Bharati Tudu, Ashutosh Tiwari The emerging technological demand of sleek, foldable and portable devices has raised a huge urge for transparent flexible electronics which requires exploration of new semiconductors beyond silicon. ZnO has the potential to be integrated into flexible electronics matrix due to its excellent electrical and optical properties. Here we report our study on ZnO thin films deposited at low temperature on polymer substrates: Polyethylene Naphthalate (PEN) and Polyimide (Kapton), using pulsed laser deposition (PLD). We have investigated the structural, electrical and optical properties of these films using a variety of techniques. Our studies show ZnO films deposited on Kapton have lower resistivity of 6 x 10$^{\mathrm{-2}} \quad \Omega $ cm and higher Hall mobility of 124 cm$^{\mathrm{2}}$/Vs compared to the films grown on PEN. Seebeck measurements show ZnO films deposited on PEN have higher Seebeck coefficient than those deposited on Kapton. ZnO films on Kapton show higher photoconductivity which is an order of magnitude higher than that of the films on PEN. To conclude, ZnO films grown on flexible substrates show good electrical and optical properties which can be used in next-generation flexible electronic devices. [Preview Abstract] |
Monday, March 13, 2017 8:48AM - 9:00AM |
A35.00005: Growth parameter control toward mobility enchancement in doped BaSnO$_{3}$ thin films Prastuti Singh, Adrian Swartz, Di Lu, Kazunori Nishio, Yasuyuki Hikita, Harold Hwang Doped BaSnO$_{3}$ is known to exhibit high electron mobility at room temperature, showing great prospects as an transparent conducting oxide.~However, when grown epitaxially on perovskite substrates, thin films exhibit reduced mobilities compared with bulk single crystals due to scattering from the formation of dislocations at the interface of the thin film and substrate. In this emerging field, correlating synthesis growth regimes, structure, and stoichiometry with transport properties is critical for developing next level oxide electronic devices. Here, we will discuss our results linking growth conditions and transport properties of La-doped BaSnO$_{3}$ (BLSO) to enhance mobility. In addition to varying standard growth parameters, we deposited BLSO on a hygroscopic pseudo-perovskite buffer layer$^{1}$. The pseudo-perovskite buffer acts as a sacrificial layer that can be selectively etched to produce conductive free-standing BLSO membranes, free of the underlying substrate. This allows us to minimize film dislocation density and examine BLSO transport properties in the limit of no substrate. $^{1}$D. Lu et al., Nat. Mater$. $DOI:10.1038/nmat4749. [Preview Abstract] |
Monday, March 13, 2017 9:00AM - 9:12AM |
A35.00006: Optimal PLD Parameters for Growth of Two Titania Phases without Change of Substrate Alexandra Gordienko, Anthony Kaye Two pure tetragonal phases of titanium dioxide – anatase and rutile – were grown on c-cut sapphire substrates via pulsed-laser deposition by changing only the growth and annealing conditions such as ambient gas pressure, substrate temperature and laser pulse repetition rate, and without changing the substrate, target, or working gas. Preliminary data for titania phase diagram is also reported. The production of multiple phases of a material using a single target and a single substrate is critical since changing either one of those can obfuscate correlations between growth conditions and the performance of the resulting film. Further, there is no prior report of the production of anatase titania on sapphire; in fact, the review presented by Janisch et al. predicted that anatase-on-sapphire was "impossible." The optimized protocols were also used for growth of titania on a collection of other substrates, creating a basis for “universal” anatase and rutile protocol that can be transferred to any substrate. For applications in which titania is used for its optical properties, sapphire substrates may be preferential, as they may significantly decrease the cost of production and increase the survivability of titania films. [Preview Abstract] |
Monday, March 13, 2017 9:12AM - 9:24AM |
A35.00007: Surface diffusion in homoepitaxial SrTiO$_{\mathrm{3}}$ thin films. Chang-Su Woo, Kanghyun Chu, Jong-Hyun Song, Chan-Ho Yang The development of growth techniques such as molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) has facilitated growths of complex oxide thin films at the atomic level ...[1-3]. Systematic studies on surface diffusion process of adatoms using theoretical and experimental methods allow us to understand growth mechanism enabling atomically flat thin film surface. In this presentation, we introduce the synthesis of homoepitaxial SrTiO$_{\mathrm{3}}$ thin films using a PLD equipped with reflection of high energy electron diffraction (RHEED). We determine the surface diffusion time as a function of growth temperature and extract the activation energy of diffusion on the surface by in-situ monitoring the RHEED intensity recovery during the film deposition. From the extracted experimental results, we discuss the microscopic mechanism of the diffusion process $.$References 1. Cui, D.-F., et al., \textit{Crystallographic and microstructural studies of BaTiO3 thin films grown on SrTiO3 by laser molecular beam epitaxy.} Journal of Vacuum Science {\&} Technology A, 1997. 15(2): p. 275-278. 2. Jiang, J.C., et al., \textit{Abrupt PbTiO3/SrTiO3 superlattices grown by reactive molecular beam epitaxy.} Applied Physics Letters, 1999. 74(19): p. 2851-2853. 3. Ohtomo, A. and H.Y. Hwang, \textit{A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface.} Nature, 2004. 427(6973): p. 423-426. [Preview Abstract] |
Monday, March 13, 2017 9:24AM - 9:36AM |
A35.00008: Optimizing electrical conductivity and optical transparency of IZO thin film deposited by radio frequency (RF) magnetron sputtering Lei Zhang Transparent conducting oxide (TCO) thin films of In2O3, SnO2, ZnO, and their mixtures have been extensively used in optoelectronic applications such as transparent electrodes in solar photovoltaic devices. In this project I deposited amorphous indium--zinc oxide (IZO) thin films by radio frequency (RF) magnetron sputtering from a In2O3--10 wt.{\%} ZnO sintered ceramic target to optimize the RF power, argon gas flowing rate, and the thickness of film to reach the maximum conductivity and transparency in visible spectrum. The results indicated optimized conductivity and transparency of IZO thin film is closer to ITO's conductivity and transparency, and is even better when the film was deposited with one specific tilted angle. [Preview Abstract] |
Monday, March 13, 2017 9:36AM - 9:48AM |
A35.00009: Dielectric and structural properties of Hf$_{1-x}$Zr$_{x}$O$_{2}$ thin film grown by pulsed laser deposition for ferroelectric oxide KyoungJun Lee, TaeYoon Lee, JaeSung Shin, SeungChul Chae Concerning ferroelectricity embedded in CMOS technology, research attention has been paid to the potential application of HfO$_{2}$ as a non-perovskite ferroelectric material. So far, HfO$_{2}$ has been considered as an alternative for the standard gate dielectric. Recently, HfO$_{2}$ demonstrated latent ferroelectricity with the typical capacitance-voltage hysteresis. In addition, the doped HfO$_{2}$ exhibited ferroelectric as well as antiferroelectric behavior. Both ferroelectric and antiferroelectric behavior of Hf$_{1-x}$Zr$_{x}$O$_{2}$ can be used as the memory device and energy harvest materials respectively. The ferroelectric behavior was observed in Hf$_{1-x}$Zr$_{x}$O$_{2}$ thin film on TiN electrode. On the other hand, it was reported that the ferroelectric behavior disappeared on Pt electrode because of its isotropic stain. In this presentation, we present the bottom electrode crystallinity dependence of ferroelectricity in Hf$_{1-x}$Zr$_{x}$O$_{2}$ thin films. We deposited Hf$_{1-x}$Zr$_{x}$O$_{2}$ on three distinct bottom electrodes, Pt(111), Pt(poly-crystalline) and ITO(111) to check strain induced ferroelectricity. Dielectric and structural properties of the Hf$_{1-x}$Zr$_{x}$O$_{2}$ thin films were investigated by P-E measurement and XRD. [Preview Abstract] |
Monday, March 13, 2017 9:48AM - 10:00AM |
A35.00010: Hydrogen Surfactant Effect on ZnO/GaN Heterostructures Growth Jingzhao Zhang, Yiou Zhang, Kinfai Tse, Junyi Zhu To grow high quality heterostructures based on ZnO and GaN, growth conditions that favor the layer by layer (Frank-Van der Merwe) growth mode have to be applied. However, if A wets B, B would not wet A without special treatments. A famous example is the epitaxial growth of Si/Ge/Si heterostructure with the help of arsenic surfactant in the late 1980s. It has been confirmed by the previous experiments and our calculations that poor crystal quality and 3D growth mode were obtained when GaN grown on ZnO polar surfaces while high quality ZnO was achieved on (0001) and (000-1)-oriented GaN. During the standard OMVPE growth processes, hydrogen is a common impurity and hydrogen-involved surface reconstructions have been well investigated experimentally and theoretically elsewhere. Due to the above facts, we proposed key growth strategies by using hydrogen as a surfactant to achieve ideal growth mode for GaN on ZnO (000-1) surface. This novel strategy may for the first time make the growth of high quality GaN single crystal on ZnO substrate possible. This surfactant effect is expected to largely improve the crystal quality and the efficiency of ZnO/GaN super lattices or other heterostructure devices. [Preview Abstract] |
Monday, March 13, 2017 10:00AM - 10:12AM |
A35.00011: Structural evolution of ultrathin film iron oxide and BiFeO$_{3}$ in ozone assisted MBE deposition Hawoong Hong, Xinyue Fang, Tai-C. Chiang Iron oxide films were grown on sapphire (0001) surfaces using nominally 100{\%} ozone. Both of monolayer-wise deposition and continuous deposition were tried to find the structures of the films at the start of the film formation. The studies utilized x-ray scattering with synchrotron radiation from the Advanced Photon Source. Consideration of substrate and film structures predicts Fe$_{2}$O$_{3}$(0001) (hematite) film formation. However, in both of the deposition modes, the initial films formed as magnetite Fe$_{3}$O$_{4}$(111). As the film growth progresses, hematite (Fe$_{2}$O$_{3}$(0001)) appears. At the later stage, the magnetite disappears and the whole film turned to hematite. The same techniques were employed for the investigation of BiFeO$_{3}$ growth. At the early stages, the layer spacing showed interesting variation through the film. The influence of the interfaces will be discussed [Preview Abstract] |
Monday, March 13, 2017 10:12AM - 10:24AM |
A35.00012: Ultrasonic Vibration Imposed on Thin Liquid Solution Films as an Effective Tool for Improved Characteristics of Ensuing Thin Solid Films Morteza Eslamian, Fatemeh Zabihi, Amin Rahimzadeh, Qin Wang, Mehran Habibi, Yu Xie Thin solid films have ubiquitous presence in various existing and emerging technologies. Solution-processed thin solid films may be fabricated by casting a liquid solution film followed by a drying step. We have developed a method in which by imposing ultrasonic vibration on the substrate, characteristics of the resulting thin solid films and the performance and reproducibility of the ensuing thin film devices, such as perovskite and polymer solar cells, are improved. To explain this, we have studied the evolution of thin liquid films, subjected to ultrasonic vibration. It is found that the vertical vibration tends to destabilize the thin liquid film, however, in low-amplitude ultrasonic vibration, the term contributing to the perturbation growth rate due to vibration, decays rapidly. Vertical vibration is found as a destabilizing force, only if the film thickness is near a critical thickness in which the destabilizing van der Waals and stabilizing gravity and surface tension forces balance one another. It is substantiated that the lateral vibration does not promote instability. In summary it is found that while imposing ultrasonic vibration may destabilize and breakup the thin liquid film, a mild and controlled vibration significantly improves the homogeneity and uniformity of the ensuing thin solid film. [Preview Abstract] |
Monday, March 13, 2017 10:24AM - 10:36AM |
A35.00013: Atomically Smooth Epitaxial Al Films for UV Plasmonics Ping-Hsiang Su, Fei Cheng, Junho Choi, Shangjr Gwo, Xiaoqin Li, Chih-Kang Shih Plasmonics is a science of manipulating light in the metal and dielectric interface. An atomically smooth epitaxial metal film is of particular importance in this field because it can significantly reduce plasmonic loss from inelastic scattering of electrons in the metal due to rough surface, crystal structure defects, and grain boundaries. Among available plasmonic metals, aluminum (Al) is of particular interest because it was demonstrated to be an excellent platform for ultraviolet (UV) plasmonics in recent years. However, Al is highly reactive with oxygen and can be rapidly oxidized once exposed to even a low partial pressure of oxygen (10$^{\mathrm{-8}}$ Torr). Therefore it will be a challenge to prepare a high-purity Al film with desired properties such as atomic smoothness and single crystallinity. In this talk I am going to report the successful growth of atomically smooth epitaxial Al films on Si(111) using a molecular beam epitaxy system. Based on the spectroscopic ellipsometry measurement, these epitaxial films show significant reduction in plasmonic loss up to a factor of two in the UV regime in comparison with the widely cited data compiled by Palik. As a result, they serve as an ideal platform for UV plasmonics. [Preview Abstract] |
Monday, March 13, 2017 10:36AM - 10:48AM |
A35.00014: Growth, structural, and magnetic properties of single-crystal full-Heusler Co$_{2}$TiGe thin films John Logan, Tobias Brown-Heft, Sean Harrington, Nathaniel Wilson, Anthony Rice, Chris Palmstrom Recent predictions have suggested that full-Heusler ferromagnetic Co$_{2}$TiGe may provide a model system for the observation of time-reversal breaking Weyl and nodal line semimetallic behavior. However, to date, few studies have examined the growth of high-quality single crystal thin films of Co$_{2}$TiGe. Consequently, this work presents the growth of Co$_{2}$TiGe thin films by molecular beam epitaxy on conductive n-InP (001) substrates as well as insulating MgO (001) substrates. The surface morphology, structural quality, and magnetic behavior are examined by reflection high-energy electron diffraction, scanning tunneling microscopy, x-ray diffraction, and SQUID magnetometry. The results reveal epitaxial smooth Co$_{2}$TiGe thin films with a terraced layer-by-layer growth mode, a saturation magnetization of \textasciitilde 1.8~$\mu$ B/formula unit, and a Curie temperature of \textasciitilde 375 K. The easy axis was found to lie in the [110] direction but magnetometry also reveals that there is only a small difference in energy between the [110] and [010] magnetization directions, in agreement with theory calculations. [Preview Abstract] |
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